Immune Protection, Natural Products, and Skin Cancer: Is There Anything New Under the Sun?

Non-melanoma skin cancers such as squamous cell carcinoma and basal cell carcinoma are the most common types of human neoplasms, representing one third of all new malignancies diagnosed in the US. The number of new cases diagnosed per year in the US alone is approaching one million and continues to rise. Ultraviolet (UV) radiation from the sun is a major cause of non-melanoma skin cancer in humans. Aside from the mutagenic effects of UV radiation, there are suggestions from clinical studies and evidence in animal models that the immune system plays an important role in preventing skin cancer development and progression, and is suppressed by cutaneous exposure to UV radiation. In this article, we review the research on new and existing agents that are being developed to protect the skin immune response from suppression by UV radiation. We also discuss the current state of knowledge regarding their mechanism of action in humans as well as animal models of photosuppression, and their efficacy in cancer prevention.